1. Field of the Invention
The present invention relates to a throttle valve control apparatus for internal combustion engine which carries out various controls on the basis of full closing reference position of a throttle valve.
2. Description of the Related Art
Conventionally as the related art, there are known, for example, a full closing position learning apparatus of throttle valve for internal combustion engine disclosed in JP-A-4-17734 by Satoru Watanabe and an output control apparatus for internal combustion engine disclosed in JP-A-4-41944 by Takeo Kume. In these apparatuses, the mechanically full closing position of the throttle valve is learned at the time of idling or turning on of the ignition switch and adopted as the full closing reference position and then control is carried out for traction and others. Furthermore, as the related art, an air intake control apparatus for internal combustion engine disclosed in JP-A-63-263239 (corresponding to U.S. Pat. No. 4,823,749) by Manfred Eisenmann et al. is known. In this control apparatus, idle speed control (hereafter also referred to as "ISC") and output control according to ordinary accelerator pedal actuation are carried out with a single throttle valve.
In the apparatus having the full closing reference position of the throttle valve set mechanically as described in the aforementioned related art papers, a position deviation occurs in the full closing reference position thereof because of assemble error from vehicle to vehicle and a change with the passage of time. Although the same signal is supplied to actuators for opening/closing the throttle valves, therefore, actual air intake flows passed through the throttle valves are, unadvantageously, not uniform. Furthermore, if the throttle valve is made fully open during engine starting, the engine is stalled. Therefore, it is impossible to find the full closing reference position by fully closing the throttle valve.